Problem: Simplify the following expression: $z = \dfrac{9}{8y} \div \dfrac{4}{8y}$
Solution: Dividing by an expression is the same as multiplying by its inverse. $z = \dfrac{9}{8y} \times \dfrac{8y}{4}$ When multiplying fractions, we multiply the numerators and the denominators. $z = \dfrac{ 9 \times 8y } { 8y \times 4}$ $z = \dfrac{72y}{32y}$ Simplify: $z = \dfrac{9}{4}$